Tackling the Carbon Footprint at Pump and Treat Projects: A Case Study in Energy Efficiency
CLU-IN Seminar
March 10, 2009
Carlos Pachon, U.S. Environmental Protection Agency
Dorothy Allen, MA Department of Environmental Protection
Doug Sutton, GeoTrans
2
Today’s Topics
U.S. Environmental Protection Agency (EPA) and Massachusetts Department of Environmental Protection (MA DEP) collaboration to:» Address energy challenges» Reduce greenhouse gas (GHG) emissions
Summary of technical issues and approach used at one Superfund site employing pump and treat (P&T) technology
Final proposal of using combined heat and power (CHP) Advancing the knowledge base for green remediation (GR)
3
Opportunities to IncreaseSustainability in Site Cleanups
Go beyond energy Exist throughout site
investigation, design, construction, operation, and monitoring
Apply to all cleanup programs
https://www.clu-in.org/greenremediation/subtab_b1.cfm https://www.clu-in.org/greenremediation/subtab_b1.cfm
4
OSWER Green Remediation“Strategy”
Benchmark and document GR best management practices
Assemble a toolkit of enablers Build networks of practitioners Develop performance metrics and tracking mechanisms
For the purpose of advancing green remediation best practices across cleanup programs, OSWER seeks to:
5
The Challenge: Carbon & Energy Footprintsof Superfund Cleanup Technologies
Technology
Pump & Treat
Thermal Desorption
Multi-Phase Extraction
Air Sparging
Soil Vapor Extraction
Technology Total
Estimated EnergyAnnual
Average(kWh*103)
489,607
92,919
18,679
10,156
6,734
618,095
Total EstimatedEnergy Use
in 2008-2030(kWh*103)
11,260,969
2,137,126
429,625
233,599
154,890
14,216,209
Annual Carbon Footprint (MT CO2)
Sum of 5 Technologies 404,411
6
Recap on Energy &Carbon Footprint Strategy
Optimize systems to maximize efficiency and return per unit of energy invested
Build renewable energy capacity at contaminated sites to power remedies
Tap into grid renewable energy portfolios Leverage carbon sequestration from soil amendment
treatment
7
EPA – MA DEP Objectives at B&M
Identify alternatives to achieve energy savings at study site that can be applied at many sites
Document approaches for carbon footprint analyses at P&T sites
Explore the potential of coupling CHP turbines to power treatment systems
Share findings and challenges yet to be overcome
Build communication among different areas of expertise such as energy, site cleanup, and project management
8
Current Site Features
32 Acres, Holbrook, MA
A) Treatment plantB) Cochato RiverC) Infiltration basinsD) Restored wetlandE) Lake HolbrookF) South Street wells
A
B
C
D
F
EE
9
Initial Conditions and Impacts
Listed on NPL in 1983
Direct discharge from lagoons and landfilling to soil, river and wetlands
Soil, groundwater, and river sediment contamination with metals, SVOCs, VOCs, PAHs, and pesticides
EPA completed RI/FS in 1983-1986
10
Remedial Action Components
Incineration of soils and river sediments (250K yd3)
» Began incineration in 1995 and completed in 1998» Excavated soil on 12.5 Acres» Buried residual ash onsite (300 yd3 stabilized)
P&T system for contaminated groundwater» Started in 1993» Initially served to treat incineration dewatering and process flows» Used from 1998 to the present for treatment of groundwater» Discharges effluent to infiltration basins
11
Remediation – 1996 to 2006
Treatment must achieve groundwater restoration at drinking water standardsTreatment must achieve groundwater restoration at drinking water standards
BB
FF
AA
A) Incinerator & restored wetlandB) Groundwater treatment plantC) Bauer, Inc.D) Excavation E) Backfilled incinerated ashF) Cochato River
EEDD
FF
BB
CC
AA
12
Pumping Rates: 75 – 140 gpm
Monthly Average Pumping Rates for Extraction Wells -- 3Q08
0
5
10
15
20
25
JUL AUG SEPT
Ga
llo
ns
pe
r M
inu
te
EW-2
EW-3
EW-4A
EW-5
EW-6
EW-7
EW-8
EW-9
13
Groundwater Contours IndicatingPlume Capture
16
CERCLA – State Obligations
For P&T remedies, the State assumes O&M after 10 years
Annual treatment plant O&M costs $3.5 million
In 2001, EPA initiated remediation system evaluations:» Automate plant: $1.3 million/yr personnel costs» Reduce process monitoring and eliminate offsite lab: $600,000/yr» Reduce security: $145,000/yr» Revise sludge disposal method: $6,000/yr» Improve LNAPL separation and disposal: $30,000/yr» Replace bio tanks with air strippers: $30,000/yr» Replace filter media: $50,000/yr
State assumes O&M on June 22, 2004
17
RSE Recommendationsand Implementation
RSE recommendations projected annual reductions at $2 million
EPA implemented most of the recommendations for annual savings of $1.5 million
State implements remaining and additional upgrades and achieves additional $1 million in annual savings:» Additional sensors and auto dialer improvements to SCADA system» Installation of computerized security system» Process sampling modified and use of off-site laboratory» Re-configure piping for GAC backwashing system» Process and site sampling plans modified» Elimination of the biocide application» Elimination of office trailers and site truck
Costs reduced from $3.5 to 1 million
18
Recent Improvementsand Annual Costs
Extraction well redevelopment
Replacement of pressure filter media (investigation of greensand and bag filters)
Utility audits: installation of more efficient lighting, motion sensors (58 MWhr/yr), VFDs for extraction, influent and pressure filter pumps (23 MWhr/yr) resulting in 7 MWhr/mo reduction
Staff: $635,000 for operations, site sampling, consulting, and reporting
Direct costs: $294,000 for materials and laboratory analysis (GAC – $65,000 for 8 x 8,000 lbs at $1/lb)
Energy: electricity $100,000 (50 MWhr/mo at $0.17 kWhr) and natural gas $23,000 (15,000 therms/year at $1.5/therm)
19
Monthly Energy Usage
0
10000
20000
30000
40000
50000
60000
70000
Feb-08
Mar-08
Apr-08
May-08
Jun-08
Jul-08
Aug-08
Sep-08
Oct-08
Nov-08
Dec-08
Jan-09
kW
Hr
0
500
1000
1500
2000
2500
3000
3500
Therm
s
kWhrTherms
20
Metals Removal System
and Neutralization
(4.25 HP)
Metals Removal System
and Neutralization
(4.25 HP)
Solids Handling6 HP plus transport
Solids Handling6 HP plus transport
Extraction System & Flow Equalization
120 gpm
(10.5 HP)
Extraction System & Flow Equalization
120 gpm
(10.5 HP)
Bio Tanks Used as Inefficient Air Strippers
(45 HP)
Bio Tanks Used as Inefficient Air Strippers
(45 HP)
Pressure Filters
(11.5 HP)
Pressure Filters
(11.5 HP)
GAC(68,000 lbs/year)
(0.5 HP)
GAC(68,000 lbs/year)
(0.5 HP)
Effluent Tank and Discharge to
Infiltration Galleries
(3 HP)
Effluent Tank and Discharge to
Infiltration Galleries
(3 HP)
Off Gas Treatment5 HP & 3,000 lbs GAC/yr
Off Gas Treatment5 HP & 3,000 lbs GAC/yr
Average motor horsepower indicated in parenthesesAverage motor horsepower indicated in parentheses
Treatment Process Flow
21
Biotanks
» Size: 172,458 gal» Detention time: 28 hours at 100 gpm» Blower size: 20 hp
22
Granular Activated Carbon
» GAC size 10,000 lbs requires 8,000 to 8,500 lbs per change-out» Pressure drop from 2 psi to 15 psi
GAC A GAC B COMMENTSFiltersorb 300 pH recommended
4/23/20046/15/2004
9/29/2004 Filtersorb 300 pH11/4/2004 Carbsorb 30pH
1/19/2005 Carbsorb 30pH3/2/2005 Carbsorb 30pH
5/9/2005- Carbsorb 30pH7/21/2005 RX-pH POOL
9/28/2005 RX-pH POOL11/3/2005 RX-pH POOL
2/1/2006 RX-pH POOL3/9/2006 RX-pH POOL
5/3/2006 RX-pH POOL6/14/2006 RX-pH POOL
9/14/2006 RX-pH POOL10/11/2006 RX-pH POOL12/7/2006 12/7/2006 RX-pH POOL3/2/2007 RX-pH POOL
3/13/2007 RX-pH POOL6/8/2007 RX-pH POOL
06/20/07 RX-pH POOL10/04/07 DSRA React carbon, pH increase
11/16/07 DSRA React carbon, pH increase01/31/08 DSRA React carbon, pH increase
02/28/08 DSRA React carbon, pH increase04/22/08 DSRA React carbon, pH increase
07/08/08 DSRA React carbon, pH increase9/23/2008 DSRA React carbon, pH increase
10/23/2008 DSRA React carbon, pH increase12/10/2008 DSRA React carbon, pH increase
2/13/2009 DSRA React carbon, pH increase
23
Planning for the Future
Long-term treatment to remove arsenic and dilute organics (naphthalene) for site restoration at drinking water standards
Effluent MCLs and GW1 to prevent contamination of infiltration basins
Additionally optimize plant/site operations » Placement of biotanks with clarifier modification» Improve GAC operations» Establish extraction well redevelopment/replacement plan» Optimize extraction well pumping» Soil sampling
Minimize energy use
Reduce emission of GHG
24
State Focus on Energy and GHG Emissions
Conservation charge: utility audits and rebates
Renewable energy charge: funding through the MTC
ISO forward capacity market
Green Communities Act: » RGGI: cap and trade allowances for generators larger than 25 MW» Utilities required to purchase “negawatt” power » Resources to communities for efficiency and renewable energy» RPS expanded to include APS for CHP
Global Warming Solutions Act: 10% to 25% below 1990 by 2020, etc. » Registration of emitters above 5,000 short tons/yr» Mass DEP voluntary reporting with the Climate Registry includes Baird & McGuire
emissions (general reporting protocol)
MEPA Policy: Governor’s zero emissions building initiative, zero net energy buildings by 2030, Clean Energy BioFuels Act
25
Concept of CHP atBaird & McGuire
Focus on energy and GHG emissions » GAC change-outs at 6.45 lbs CO2/lb GAC
» Biotank energy requirements
Elimination of biotanks and GAC units
Addition of air stripping at elevated temperature
Addition of engine or turbine to provide heat and power
Provide for maximum heat recovery
26
Parameters for the Study
Carbon parameters» Electricity: 1.48 lbs of CO2 per kWh (GRID 2005 for MA)
» Natural gas: 12.2 lbs of CO2 per therm (www.nrel.gov/lci)
» GAC: 6.45 lbs of CO2 per pound of GAC (discussion point)
» Travel: 40 lbs of CO2 per site visit (based on approximately 2
gallons of gas per visit)
Cost parameters» Electricity: $0.17/kWh (bills)» Natural gas: $1.50/therm (bills)» GAC: $1.04/lb (contract estimate)» Service tech visit: $450 per visit
27
Breakdown of Current CarbonFootprint and O&M Cost
0
50
100
150
200
250
Extrac
tion
& Equ
ilizat
ion
Met
als R
emov
al
Inef
ficien
t Stri
pping
Vapor
Tre
atm
ent
Press
ure
Filters
GAC
Effluen
t Pum
ps &
Sum
p
O&M L
abor
Buildin
g
To
ns
of
CO
2/y
r
$0
$100,000
$200,000
$300,000
$400,000
$500,000
$600,000
$700,000
An
nu
al C
os
t
Tons of CO2/yr
Annual Cost
Total O&M Cost: $784,000 per year
Total Carbon Footprint: 787 tons of CO2 per year
Total O&M Cost: $784,000 per year
Total Carbon Footprint: 787 tons of CO2 per year
O&M costs and carbon footprint (for remainder of presentation) are for O&M of treatment plant and do not include other site activities including groundwater sampling
O&M costs and carbon footprint (for remainder of presentation) are for O&M of treatment plant and do not include other site activities including groundwater sampling
28
Preliminary Analysis
The GAC has a high carbon footprint and a high cost (largely due to frequent change-outs)
O&M labor costs are high, but the carbon footprint is relatively low
Previous evaluations suggest capture is adequate but not much room for reducing extraction rates. VFD’s on all extraction pumps, so assumption is that there is little room for reducing energy usage for extraction
Inefficient air stripping has a substantial footprint
Building footprint is also significant (18,700 therms of NG for heating, 75,000 kWh per year for ventilation, lighting, etc.)
29
Options
Eliminate stripping and go to GAC-only for treatment of organics, attempt to decrease GAC change-out frequency
Eliminate GAC and go with stripping only
Enhance stripping with waste heat from a combined heat and power unit
Consider alternatives for building heating/cooling
30
Breakdown for Various Options
554
661665
$720,000
$739,000$756,000
400
450
500
550
600
650
700
GAC-Only GAC-Only, 50% Reduction Air Stripping
To
ns
of
CO
2/y
r
$500,000
$550,000
$600,000
$650,000
$700,000
$750,000
$800,000
An
nu
al C
os
t
Tons of CO2/yr
Annual Cost
31
Stripping Effectiveness and Water Temperature
Naphthalene Effluent Concentration vs. Water Temperature with Water Flow of 120 gpm, Air Flow of 900 cfm, 6 Trays, and an Influent Concentration of 800 ug/L
0
50
100
150
200
250
300
350
400
450
500
40 50 60 70 80 90 100
Influent Water Temperature (F)
Eff
lue
nt
Co
nc
en
tra
tio
n (
ug
/L)
Results based on Carbonair software for STAT 180 unit
32
Heat-Enhanced Air Stripping
Water From Metals Removal System
120 gpm 45 F
Water From Metals Removal System
120 gpm 45 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
Heat Source
0.515 MMBtuh
Heat Source
0.515 MMBtuh
1.96 MMBtuh1.96 MMBtuh
Sensible and Latent Heat Loss2.4 MMBtuh + 0.08 MMBtuh for heating off-gas
Sensible and Latent Heat Loss2.4 MMBtuh + 0.08 MMBtuh for heating off-gas
33
Combined Heat and Power
Generate electricity on-site with a natural gas powered generator
Rather than discharge heat to the atmosphere, use it for beneficial use
Results in increased overall efficiency
Only makes sense if electrical demand and heating demand are present and appropriate
34
CHP Heat-Enhanced Air Stripping
Water From Metals Removal System
120 gpm 45 F
Water From Metals Removal System
120 gpm 45 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
75 kW CHP Unit
Uses:60,800 therms NG/year
Generates:506,400 kWh/year
0.435 MMBtuh
75 kW CHP Unit
Uses:60,800 therms NG/year
Generates:506,400 kWh/year
0.435 MMBtuh
1.96 MMBtuh1.96 MMBtuh
Sensible and Latent Heat Loss2.4 MMBtuh
(plus 0.08 MMBtuh to heat off-gas)
Sensible and Latent Heat Loss2.4 MMBtuh
(plus 0.08 MMBtuh to heat off-gas)
Small Boiler
Uses:7,000 therms NG/year
Generates:0.08 MMBtuh
Small Boiler
Uses:7,000 therms NG/year
Generates:0.08 MMBtuh
35
CHP Option vs. Boiler Option
CHP Option Uses:
» 60,800 therms of NG per year
CHP Generates:» 506,400 kWh per year» 0.435 MMBtuh
(a boiler supplies additional0.08 MMBtuh)
Boiler Option Uses:» 47,500 therms of NG per year
Boiler Generates:» 0.51 MMBtuh
823
665
573
$756,000
$777,600
$744,500
400
450
500
550
600
650
700
750
800
850
CHP Boiler GAC-Only
To
ns
of
CO
2/yr
$500,000
$550,000
$600,000
$650,000
$700,000
$750,000
$800,000
An
nu
al C
ost
Tons of CO2/yr
Annual Cost
36
Water Source Heat Pumps(Heating Mode Shown)
HVACAir/RefrigerantHeat Exchanger
(Condenser)
HVACAir/RefrigerantHeat Exchanger
(Condenser)
External Heat Exchanger
(protects heat pump)
External Heat Exchanger
(protects heat pump)
Refrigerant CompressorRefrigerant Compressor
Source of water
Source of water
Discharge of water
(now cooler)
Discharge of water
(now cooler)
Internal Water/Refrigerant
Heat Exchanger (Evaporator)
Internal Water/Refrigerant
Heat Exchanger (Evaporator)
Expansion Valve
Expansion Valve
Hot Vapor RefrigerantHot Vapor Refrigerant
Hot Liquid RefrigerantHot Liquid Refrigerant
Cool Liquid RefrigerantCool Liquid Refrigerant
Cool Vapor RefrigerantCool Vapor Refrigerant
Similar concept to air conditioner or refrigerator but
» Heats instead of cools air» Uses water not air as the heat source
Heat from water vaporizes refridgerant Heat from condensing refridgerant is transferred to building via HVAC system Heat is transferred via vaporization/condensation of refridgerant
Closed water loop
Closed water loop
Packaged UnitPackaged Unit
37
CHP & Heat Pump
Water From Metals Removal System
120 gpm 45 F
Water From Metals Removal System
120 gpm 45 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Air Stripper
900 cfm Air at 45 F
Water at 85 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
Heat Exchanger
Th,i = 82.7 FTh,o= 50 FTc,i = 45 F
Tc,o= 77.7 F
75 kW CHP Unit
Uses:67,100 therms NG/year
Generates:558,500 kWh/year
0.48 MMBtuh
75 kW CHP Unit
Uses:67,100 therms NG/year
Generates:558,500 kWh/year
0.48 MMBtuh
1.96 MMBtuh1.96 MMBtuh
Sensible & Latent Heat LossSensible & Latent Heat LossHeat Pump
Ti = 50 FTo= 40 F
COP = 3.9
Uses:Power = 18kW
Generates:0.245 MMBtuh
Heat Pump
Ti = 50 FTo= 40 F
COP = 3.9
Uses:Power = 18kW
Generates:0.245 MMBtuh
Building Heating(displace 18,700 therms of NG)
Building Heating(displace 18,700 therms of NG)
38
CHP Option With and Without Heat Pump
514
665
573
$756,000
$729,300$744,500
400
450
500
550
600
650
700
CHP CHP & Heat Pump GAC-Only
To
ns
of
CO
2/yr
$500,000
$550,000
$600,000
$650,000
$700,000
$750,000
$800,000
An
nu
al C
ost
Tons of CO2/yr
Annual Cost
Heat Pump:» Adds electrical load so that
CHP unit operates at full load
» Displaces 18,700 therms of NG/yr
» Reduces carbon footprint for heating building by about 30 tons of CO2/yr
39
% Reductions for Carbon Footprint and Cost
% Reduction
OptionCarbon
FootprintAnnual O&M
Cost
GAC-only 16% 4%
Air Stripping 16% 6%
CHP 27% 5%
GAC-only (50% reduction)
29% 9%
CHP & Heat pump 35% 7%
40
Payback of Various Options
400
450
500
550
600
650
700
750
800
850
Baseline GAC-Only Air Stripping CHP GAC-Only 50%Reduction
CHP & HeatPump
To
ns
of
CO
2/yr
0
2
4
6
8
10
12
Pa
yb
ac
k (
ye
ars
)
Tons of CO2/yr
Payback
41
Conclusions Regarding Site
Investigate GAC performance
» Clarifier sizing» Metals removal chemistry» Filter effectiveness» Backwashing effectiveness
Depending on GAC results pilot air stripping with and without heating
Depending on pilot results consider CHP option but concern regarding potential future reduced standards for naphthalene
Consider water source heat pump for building heat regardless
42
Conclusions RegardingFootprint Analysis
Labor is high cost but has a relatively low footprint
Electricity and energy is relatively low cost but has a high footprint
Materials can have a high footprint
Footprint for travel, electricity, and natural gas are relatively straightforward to calculate for various options
Footprint for materials (e.g., GAC) can be substantial but are uncertain without manufacturer input… accurate carbon footprinting for groundwater remediation requires reliable carbon footprints for materials (GAC, chemicals, etc.)
GAC footprint is not well understood
» 6.45 lbs of CO2 per pound of GAC from Goldblum, et al.
» May be substantially more than 10 lbs of CO2 per pound of GAC for virgin, coal-based
carbon but could be substantially lower for regenerated carbon» Emphasis on using renewable resource for GAC feedstock
43
Conclusions Regarding Technological Applications
CHP (combined with heat exchangers) is a carbon and energy efficient method of heating process water » May be beneficial to some biological treatment systems» Enhances stripping efficiency» In-situ remedies (?)
Optimize traditional treatment components when comparing to new or more complex treatment approaches
CHP-enhanced stripping may be even more appropriate for contaminants such as MTBE that are difficult to remove via stripping and GAC
Appropriately consider disadvantages associated with heating water before implementing a treatment approach that requires heating » Increased potential for fouling» System has to “come up to temperature” before effective treatment can begin
Heat pumps for building heating and cooling may be appropriate at many P&T sites
44
Conclusions Regarding Technological Applications
Questions ?
Carlos Pachon, [email protected]
Dorothy Allen, [email protected]
Doug Sutton, [email protected]
45 www.clu-in.org/greenremediation
EPA Resources on Green Remediation
46
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